JP6303693B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus.

  In a conventional image forming apparatus such as a copying machine or a printer, a technique described in Patent Document 1 below is conventionally known as a developing device that develops a latent image into a visible image.

  Japanese Patent Application Laid-Open No. 2008-268576 as Patent Document 1 discloses a developer peeling supply member for a developing roll (72) having a developing magnetic pole (96) and two magnetic poles (98, 100) adjacent to both sides thereof. (78) describes a technique for supplying and peeling the developer by disposing the sleeve (92) on the downstream side in the rotation direction with respect to the point B at which the magnetic flux density in the normal direction becomes substantially zero. Has been.

JP 2008-268576 A ("0036" to "0043", FIGS. 3 to 5)

  An object of the present invention is to reinforce the magnetic force of the developing magnetic pole with a simple configuration.

In order to solve the technical problem, the developing device of the invention according to claim 1 comprises:
A latent image formed on the surface of the image carrier, comprising: a magnet member that is supported in a non-rotatable manner; and a rotating member that surrounds the outer periphery of the magnet member and rotates while holding a developer on the surface. A developer holder for developing
A developing magnetic pole disposed at a position corresponding to the image carrier, and an adjacent magnetic pole disposed adjacent to the developing magnetic pole with respect to the rotation direction of the rotating member and having a polarity opposite to the developing magnetic pole. The magnet member;
A magnetic member disposed opposite to the adjacent magnetic pole and having magnetism;
The surface of the rotating member is disposed on the upstream side of the position where the image holding member and the rotating member face each other with respect to the rotation direction of the rotating member, with a gap between the rotating member and the rotating member. A regulating member that regulates the amount of developer held in
In a cross section perpendicular to the rotation axis of the developer holder, an angular region having a magnetic flux density that is half or more of the peak value of the magnetic flux density of the magnetic field formed in the normal direction of the developer holder, and the rotation member The magnetic member having a cross-sectional area of more than half of a cross-sectional area of a region surrounded by a position twice the radius and a position corresponding to the interval between the rotating member and the regulating member;
It is provided with.

The invention according to claim 2 is the developing device according to claim 1,
In an area having an angle having a magnetic flux density more than half of the peak value of the magnetic flux density of the magnetic field formed in the normal direction of the developer holder, and in an area closer to twice the radius of the rotating member The magnetic member disposed,
It is provided with.

The invention described in claim 3 is the developing device according to claim 1 or 2,
The surface of the rotating member is disposed on the upstream side of the position where the image holding member and the rotating member face each other with respect to the rotation direction of the rotating member, with a gap between the rotating member and the rotating member. A regulating member that regulates the amount of developer held in
Compared to the gap between the rotating member and the regulating member, the magnetic member in which the gap between the rotating member and the rotating member is set wide,
It is provided with.

In order to solve the technical problem, an image forming apparatus according to a fourth aspect of the present invention provides:
An image carrier,
A latent image forming apparatus for forming a latent image on the surface of the image carrier;
The developing device according to any one of claims 1 to 3 , wherein a latent image on the surface of the image carrier is developed into a visible image;
A transfer device for transferring a visible image of the surface of the image carrier to a medium;
A fixing device for fixing a visible image on the surface of the medium;
It is provided with.

According to the first and fourth aspects of the invention, it is possible to reinforce the magnetic force of the developing magnetic pole with a simple configuration as compared with the case without the configuration of the present invention.
Further, according to the first and fourth aspects of the present invention, the magnetic capacity of the magnetic member can be ensured as compared with the case where the configuration of the present invention is not provided.
According to the second aspect of the present invention, the magnetic force of the adjacent magnetic pole can be efficiently concentrated by the magnetic member as compared with the case where the configuration of the present invention is not provided.
According to the third aspect of the present invention, the inside of the machine can be reduced from being dirty as compared with the case where the configuration of the present invention is not provided .

FIG. 1 is an explanatory diagram of the image forming apparatus according to the first embodiment. FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to the first embodiment. FIG. 3 is an explanatory diagram of the developing device according to the first embodiment. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is an explanatory diagram of the magnetic member of Example 1, corresponding to FIG. FIG. 6 is an explanatory diagram of the estimated lines of magnetic force of the magnetic member according to the first embodiment. FIG. 7 is an explanatory diagram of magnetic force distribution in the developer holder of Example 1. FIG. FIG. 8 is an explanatory diagram of the experimental results of the experimental example, and is a bar graph of the experimental results obtained by measuring the increase in the magnetic flux density of the developing magnetic pole for experimental example 1, comparative example 1, and comparative example 2. FIG. 9 is an explanatory diagram of the experimental results of the experimental example, in which the horizontal axis represents the peak value of the magnetic flux density of the transport magnetic pole and the vertical axis represents the increase in the magnetic flux density of the developing magnetic pole.

Next, examples as specific examples of embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
In order to facilitate understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the left-right direction is the Y-axis direction, the up-down direction is the Z-axis direction, and arrows X, -X, Y, -Y, The direction indicated by Z and -Z or the indicated side is defined as the front side, the rear side, the right side, the left side, the upper side, the lower side, or the front side, the rear side, the right side, the left side, the upper side, and the lower side, respectively.
In the figure, “•” in “○” means an arrow heading from the back of the page to the front, and “×” in “○” is the front of the page. It means an arrow pointing from the back to the back.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

FIG. 1 is an explanatory diagram of the image forming apparatus according to the first embodiment.
FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to the first embodiment.
In FIG. 1, a copier U as an example of an image forming apparatus according to a first exemplary embodiment of the present invention is an example of a recording unit, and includes a printer unit U1 as an example of an image recording apparatus. A scanner unit U2 as an example of a reading unit and an example of an image reading device is supported on the upper portion of the printer unit U1. An auto feeder U3 as an example of a document transport device is supported on the upper portion of the scanner unit U2. The scanner unit U2 of the first embodiment supports a user interface UI as an example of an input unit. The user interface UI can be operated by the operator by inputting the user interface UI.

  A document tray TG1 as an example of a medium container is disposed on the upper part of the auto feeder U3. A plurality of documents Gi to be copied can be stacked and stored in the document tray TG1. A document discharge tray TG2 as an example of a document discharge unit is formed below the document tray TG1. A document transport roll U3b is disposed between the document tray TG1 and the document discharge tray TG2 along the document transport path U3a.

A platen glass PG as an example of a transparent document table is disposed on the upper surface of the scanner unit U2. In the scanner unit U2 of the first embodiment, a reading optical system A is disposed below the platen glass PG. The optical system A for reading in Example 1 is supported so as to be movable in the left-right direction along the lower surface of the platen glass PG. The reading optical system A is normally stopped at the initial position shown in FIG.
On the right side of the optical system A for reading, an imaging element CCD as an example of an imaging member is arranged. An image processing unit GS is electrically connected to the image sensor CCD.
The image processing unit GS is electrically connected to the writing circuit DL of the printer unit U1. The writing circuit DL is electrically connected to LED heads LHy, LHm, LHc, and LHk as an example of a latent image forming apparatus.

Above each of the LED heads LHy to LHk, photosensitive drums PRy, PRm, PRc, and PRk as an example of an image holding member are disposed.
Charging rolls CRy, CRm, CRc, CRk as an example of a charger are arranged to face each of the photosensitive drums PRy to PRk. A charging voltage is applied from the power supply circuit E to the charging rolls CRy to CRk. The power supply circuit E is controlled by a controller C as an example of a control unit. The controller C performs various controls by transmitting and receiving signals to and from the image processing unit GS and the writing circuit DL.
In the writing areas Q1y, Q1m, Q1c, Q1k set on the downstream side of the charging rolls CRy to CRk with respect to the rotation direction of the photosensitive drums PRy to PRk, LEDs are formed with respect to the surfaces of the photosensitive drums PRy to PRk. Write light is emitted from the heads LHy to LHk.
The developing devices Gy, Gm, Gc, and Gk are provided in the developing regions Q2y, Q2m, Q2c, and Q2k set downstream of the writing regions Q1y to Q1k with respect to the rotation direction of the photosensitive drums PRy to PRk. The drums PRy to PRk are arranged to face the surface.

Primary transfer areas Q3y, Q3m, Q3c, and Q3k are set on the downstream side of the development areas Q2y to Q2k with respect to the rotation direction of the photosensitive drums PRy to PRk. In the primary transfer regions Q3y to Q3k, they are in contact with an intermediate transfer belt B as an example of an intermediate transfer member. In the primary transfer areas Q3y, Q3m, Q3c, and Q3k, primary transfer rolls T1y, T1m as an example of a primary transfer unit are disposed on the opposite side of the photosensitive drums PRy to PRk across the intermediate transfer belt B. T1c and T1k are arranged.
Drum cleaners CLy, CLm, CLc, and CLk as an example of an image carrier cleaner are disposed downstream of the primary transfer regions Q3y to Q3k with respect to the rotation direction of the photosensitive drums PRy to PRk. .

  A belt module BM as an example of an intermediate transfer device is disposed above the photosensitive drums PRy to PRk. The belt module BM includes the intermediate transfer belt B. The intermediate transfer belt B includes a driving roll Rd as an example of a driving member, a tension roll Rt as an example of a stretching member, a walking roll Rw as an example of a meandering correction member, and an idler roll Rf as an example of a driven member. It is rotatably supported by a backup roll T2a as an example of a counter member in the secondary transfer region and primary transfer rolls T1y, T1m, T1c, T1k.

On the opposite side of the backup roll T2a across the intermediate transfer belt B, a secondary transfer roll T2b as an example of a secondary transfer member is disposed. The backup roll T2a and the secondary transfer roll T2b constitute a secondary transfer device T2. A secondary transfer region Q4 is formed by a region where the secondary transfer roll T2b and the intermediate transfer belt B face each other.
The primary transfer rolls T1y to T1k, the intermediate transfer belt B, the secondary transfer unit T2, and the like constitute a transfer device T1 + T2 + B of Example 1 that transfers an image formed on the photosensitive drums PRy to PRk to a medium. .

A belt cleaner CLb, which is an example of an intermediate transfer member cleaner, is disposed downstream of the secondary transfer region Q4 with respect to the rotation direction of the intermediate transfer belt B.
Above the belt module BM, cartridges Ky, Km, Kc, and Kk as an example of a developer container are disposed. Each of the cartridges Ky to Kk contains a developer to be supplied to the developing devices Gy to Gk. The cartridges Ky to Kk and the developing devices Gy to Gk are connected by a developer replenishing device (not shown).

In the lower part of the printer unit U1, paper feed trays TR1 to TR3 are arranged as an example of a medium container. The paper feed trays TR1 to TR3 are detachably supported in the front-rear direction by a guide rail GR as an example of a guide member. Sheets T as an example of a medium are accommodated in the sheet feed trays TR1 to TR3.
A pickup roll Rp as an example of a medium take-out member is disposed on the upper left side of the paper feed trays TR1 to TR3. On the left side of the pick-up roll Rp, a separating roll Rs as an example of a separating member is disposed.
On the left side of each of the paper feed trays TR1 to TR3, a medium conveyance path SH extending upward is formed. A plurality of transport rolls Ra as an example of a medium transport member are arranged in the transport path SH. In the transport path SH, a registration roll Rr as an example of a feeding member is disposed on the downstream side in the transport direction of the sheet S and on the upstream side of the secondary transfer region Q4.

A fixing device F is disposed above the secondary transfer region Q4. The fixing device F includes a heating roll Fh as an example of a heating member and a pressure roll Fp as an example of a pressure member. A fixing region Q5 is configured by a contact region between the heating roll Fh and the pressure roll Fp.
A discharge roller Rh as an example of a medium conveying member is disposed obliquely above the fixing device F. A discharge tray TRh as an example of a medium discharge portion is formed on the right side of the discharge roller Rh.

(Description of image forming operation)
The plurality of documents Gi stored in the document tray TG1 sequentially passes through the document reading position on the platen glass PG and is discharged to the document discharge tray TG2.
When the automatic feeder U3 is used to automatically convey and copy a document, each document that sequentially passes through the reading position on the platen glass PG with the reading optical system A stopped at the initial position. Gi is exposed.
When the operator places the document Gi on the platen glass PG by hand, the optical system A for reading moves in the left-right direction, and the document on the platen glass PG is scanned while being exposed.

The reflected light from the original document Gi passes through the optical system A for reading and is condensed on the image sensor CCD. In the imaging device CCD, the reflected light of the original collected on the imaging surface is converted into electrical signals of red: R, green: G, blue: B.
The image processing unit GS converts RGB electrical signals input from the image sensor CCD into black: K, yellow: Y, magenta: M, cyan: C image information and temporarily stores them. The image processing unit GS outputs the temporarily stored image information to the writing circuit DL as image information for forming a latent image at a preset time.
When the original image is a single color image, so-called monochrome, image information of only black: K is input to the writing circuit DL.

The writing circuit DL has driving circuits for respective colors Y, M, C, and K (not shown), and an LED head arranged for each color at a preset time with a signal corresponding to input image information. Output to LHy to LHk.
The surface of each photoconductor drum PRy to PRk is charged by charging rolls CRy to CRk. The LED heads LHy to LHk form electrostatic latent images on the surfaces of the photosensitive drums PRy to PRk in the writing areas Q1y to Q1k. The developing devices Gy to Gk develop the electrostatic latent images on the surfaces of the photosensitive drums PRy to PRk into toner images as an example of visible images in the development areas Q2y to Q2k. When the developer is consumed in the developing devices Gy to Gk, the developers are supplied from the cartridges Ky to Kk to the developing devices Gy to Gk according to the consumption amount.

  The toner images on the surfaces of the photosensitive drums PRy to PRk are conveyed to the primary transfer areas Q3y, Q3m, Q3c, and Q3k. A primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied to each of the primary transfer rolls T1y to T1k from a power supply circuit E at a preset time. Therefore, in the primary transfer areas Q3y to Q3k, the toner images on the photosensitive drums PRy to PRk are sequentially transferred to the intermediate transfer belt B by the primary transfer voltage. In the case of a K-color single-color image, only the K-color toner image is transferred from the K photosensitive drum PRk to the intermediate transfer belt B.

  The toner images on the photosensitive drums PRy to PRk are primarily transferred onto an intermediate transfer belt B as an example of an intermediate transfer member by the primary transfer rolls T1y, T1m, T1c, and T1k. Residues and deposits on the surface of the photoconductor drums PRy to PRk after the primary transfer are cleaned by the photoconductor cleaners CLy to CLk. The cleaned surfaces of the photosensitive drums PRy to PRk are recharged by charging rolls CRy to CRk.

The sheets S in the respective sheet feeding trays TR1 to TR3 are taken out by the pickup roll Rp at a preset sheet feeding timing. The sheets S picked up by the pick-up roll Rp are separated one by one by the rolling roll Rs when picked up in a state where a plurality of sheets S are overlapped. The sheet S that has passed the separating roll Rs is conveyed to the registration roll Rr by a plurality of conveying rolls Ra.
The registration roll Rr sends out the sheet S in accordance with the timing when the toner image on the surface of the intermediate transfer belt B moves to the secondary transfer region Q4.

The toner image on the surface of the intermediate transfer belt B is transferred to the sheet S fed from the registration roll Rr by the secondary transfer voltage applied to the secondary transfer roll T2b when passing through the secondary transfer area Q4. .
The surface of the intermediate transfer belt B after passing through the secondary transfer region Q4 is cleaned by removing residual toner by the belt cleaner CLb.
When the sheet S that has passed through the secondary transfer area Q4 passes through the fixing area Q5, the toner image is heated and pressed by the fixing device F to be fixed.
The recording sheet S on which the toner image is fixed is discharged to the paper discharge tray TRh by the discharge roller Rh.

(Description of developing device)
FIG. 3 is an explanatory diagram of the developing device according to the first embodiment.
4 is a cross-sectional view taken along line IV-IV in FIG.
Next, the developing devices Gy, Gm, Gc, and Gk according to the first embodiment of the present invention will be described. Since the developing devices Gy, Gm, Gc, and Gk of the respective colors are configured in the same manner, the development of the Y color is performed. Only the apparatus Gy will be described in detail, and detailed descriptions of the other color developing apparatuses Gm, Gc, Gk will be omitted.
3 and 4, the developing device Gy disposed to face the photosensitive drum PRy has a developing container V that stores a two-component developer containing toner and a carrier. In FIG. 3, the developing container V has a lower container body 1. A container cover 2 as an example of a lid member is supported on the upper part of the container body 1. The container cover 2 closes the upper surface of the container body 1.

3 and 4, the container main body 1 is formed with a developing roll chamber 4 as an example of a developer holding member accommodating portion at the upper left portion inside. A supply chamber 6 as an example of a first storage chamber is formed below the developing roll chamber 4. The supply chamber 6 is connected to the developing roll chamber 4. On the right side of the supply chamber 6, a stirring chamber 7 as an example of a second storage chamber is formed.
The supply chamber 6 and the stirring chamber 7 are partitioned by a partition wall 8 as an example of a partition member. In FIG. 4, a first inflow portion 8 a that connects the supply chamber 6 and the stirring chamber 7 is formed in front of the partition wall 8 as an example of a first connection portion. In the first embodiment, the first inflow portion 8 a is disposed in front of the front end of the developing roll chamber 4. In addition, a second inflow portion 8 b that connects the supply chamber 6 and the stirring chamber 7 is formed behind the partition wall 8 as an example of a second connection portion.

  The developing roll chamber 4 accommodates a developing roll R0y as an example of a developer holding body. The developing roll R0y has a part of the upper left outer surface facing the photosensitive drum PRy. The developing roll R0y has a magnet roll 11 as an example of a magnet member. In FIG. 4, the magnet roll 11 is supported by the developing container V so as not to rotate. 3 and 4, a developing sleeve 12 as an example of a rotating member is disposed on the outer periphery of the magnet roll 11. The developing sleeve 12 is rotatably supported by the developing container V. A gear G0 as an example of a drive transmission member is supported at the rear end of the developing sleeve 12. The gear G0 is configured to be able to transmit drive from a motor (not shown) as an example of a drive source. In the developing device Gy of Example 1, when the drive is transmitted from the motor, the developing sleeve 12 rotates in the same direction as the moving direction of the surface of the photosensitive drum PRy in the developing region Q2y.

Below the developing roll chamber 4, a trimmer 13 as an example of a regulating member having a layer thickness is disposed. The trimmer 13 of Example 1 is formed in a columnar shape extending in the front-rear direction. The trimmer 13 is supported with respect to the developing sleeve 12 in a non-rotatable state with a predetermined gap.
The magnet roll 11 is provided with a developing magnetic pole S1 corresponding to the developing region Q2y. Further, a trimming magnetic pole N2 as an example of a magnetic pole for regulating the layer thickness is provided at a position facing the trimmer 13. The trimming magnetic pole N2 is composed of a magnetic pole having a polarity opposite to that of the developing magnetic pole S1. A transport magnetic pole N1 having a polarity opposite to that of the developing magnetic pole S1 is provided on the downstream side of the developing magnetic pole S1 with respect to the rotation direction of the developing sleeve 12. A pick-off magnetic pole S2 as an example of a magnetic pole for detachment of the developer is provided on the downstream side of the conveying magnetic pole N1 with respect to the rotation direction of the developing sleeve 12. The pick-off magnetic pole S2 is composed of a magnetic pole having a polarity opposite to that of the carrier magnetic pole N1. A pickup magnetic pole S3 as an example of a magnetic pole for attracting the developer is provided on the downstream side of the pick-off magnetic pole S2 and the upstream side of the trimming magnetic pole N2 with respect to the rotation direction of the developing sleeve 12. The pickup magnetic pole S3 is composed of a magnetic pole having the same polarity as that of the pick-off magnetic pole S2 and having a polarity opposite to that of the trimming magnetic pole N2.

3 and 4, a supply auger 16 as an example of a first conveying member is disposed in the supply chamber 6. The supply auger 16 has a rotating shaft 16a extending in the front-rear direction. A spiral conveying blade 16b is supported on the outer periphery of the rotating shaft 16a. A gear G1 as an example of a drive transmission member is supported at the rear end of the rotating shaft 16a.
In the stirring chamber 7, a stirring auger 17 as an example of a second transport member is disposed. As with the supply auger 16, the stirring auger 17 includes a rotating shaft 17a, a conveying blade 17b, and a gear G2. The gears G0 to G2 mesh with each other.
In FIG. 4, a supply port 7 a for supplying developer from the cartridge Ky is formed at the rear of the stirring chamber 7.

(Developer function)
In the developing devices Gy to Gk having the above-described configuration, when image formation is started, the motor is driven to rotate the augers 16 and 17 and the developing rolls R0y to R0k. In the first embodiment, when the supply auger 16 rotates, the supply auger 16 conveys the developer in the supply chamber 6 while stirring the developer from the first inflow portion 8a toward the second inflow portion 8b as indicated by an arrow Ya. To do. The developer conveyed to the second inflow portion 8b flows into the stirring chamber 7 through the second inflow portion 8b. When the stirring auger 17 rotates, the stirring auger 17 conveys the developer in the stirring chamber 7 while stirring from the second inflow portion 8b toward the first inflow portion 8a as indicated by an arrow Yb. The developer conveyed to the first inflow portion 8a flows into the supply chamber 6 through the first inflow portion 8a. Therefore, the supply chamber 6 and the stirring chamber 7 constitute a circulation chamber 6 + 7.

  The developer in the supply chamber 6 is attracted to the developing sleeve 12 by the magnetic force of the pickup magnetic pole S3. When the developer adsorbed on the developing sleeve 12 passes through the trimmer 13, only a preset developer corresponding to the gap between the trimmer 13 and the developing sleeve 12 passes. The developer that has passed through the trimmer 13 develops the latent images on the photosensitive drums PRy to PRk in the development areas Q2y to Q2k. The developer that has not been used for development is conveyed while adsorbed on the surface of the developing sleeve 12 by a magnetic field between the developing magnetic pole S1 and the conveying magnetic pole N1, a magnetic field between the conveying magnetic pole N1 and the pick-off magnetic pole S2, or the like. . Between the pick-off magnetic pole S2 and the pick-up magnetic pole S3 having the same polarity, the magnetic force that attracts the developer to the developing sleeve 12 decreases. Therefore, the developer adsorbed on the surface of the developing sleeve 12 is separated from the developing sleeve 12 between the pick-off magnetic pole S2 and the pick-up magnetic pole S3 and returned to the circulation chamber 6 + 7.

(Description of magnetic member)
FIG. 5 is an explanatory diagram of the magnetic member of Example 1, corresponding to FIG.
3 and 5, in the developing device Gy of the first embodiment, a magnetic shaft 21 as an example of a magnetic member is supported so as to face a transport magnetic pole N1 as an example of an adjacent magnetic pole adjacent to the developing magnetic pole S1. . The magnetic shaft 21 of Example 1 is made of iron as an example of a magnetic body. In the first embodiment, the magnetic shaft 21 is formed in a columnar shape like the trimmer 13. In Example 1, a cylinder having a diameter of 6 mm was used as the magnetic shaft 21 as an example.
In FIG. 5, the magnetic shaft 21 of the first embodiment is an angle region having a magnetic flux density that is more than half the peak value of the magnetic flux density of the magnetic field 22 formed by the transport magnetic pole N1 in the normal direction of the developing roll R0y, so-called transport. It arrange | positions inside the half value width 23 of the magnetic pole N1.

Further, as shown in FIG. 5, the magnetic shaft 21 of the first embodiment is disposed in a region closer to the position 24 that is twice the radius of the developing sleeve 12.
Furthermore, in the magnetic shaft 21 of Example 1, as shown in FIG. 5, the magnetic shaft 21 is disposed at a position farther from the position 26 of the gap between the developing sleeve 12 and the trimmer 13. That is, the gap 26 between the developing sleeve 12 and the magnetic shaft 21 is set wider than the gap between the developing sleeve 12 and the trimmer 13.
Further, as shown in FIG. 5, in the cross section perpendicular to the rotation axis of the developing roll R0y, the range of the half width 23, the position 24 twice the radius of the developing sleeve 12, and the gap between the developing sleeve 12 and the trimmer 13 The magnetic shaft 21 is set to have a cross-sectional area of more than half of the cross-sectional area of the region 27 surrounded by the position 26.

(Description of function of magnetic member)
FIG. 6 is an explanatory diagram of the estimated lines of magnetic force of the magnetic member according to the first embodiment.
In the developing device Gy of Example 1 having the above-described configuration, the magnetic shaft 21 is disposed on the transport magnetic pole N1 adjacent to the developing magnetic pole S1. In FIG. 6, in the conventional configuration in which the magnetic shaft 21 is not provided, a magnetic force line 31 as shown by the solid line in FIG. 6 is established between the developing magnetic pole S1 and the transport magnetic pole N1. Here, when the magnetic shaft 21 is disposed so as to face the transport magnetic pole N1 as in the first embodiment, the magnetic force lines 32 change in such a manner that the magnetic force lines 32 are attracted to the magnetic shaft 21 as shown by broken lines in FIG. It is estimated to be. Therefore, in the vicinity of the developing magnetic pole S1, the magnetic force line 32 has a higher magnetic flux density in the normal direction, and the magnetic force in the normal direction is improved.

FIG. 7 is an explanatory diagram of magnetic force distribution in the developer holder of Example 1. FIG.
FIG. 7 shows the position along the direction opposite to the rotation direction of the developing sleeve 12 on the abscissa and the ordinate on the point where the magnetic force in the normal direction is zero between the transport magnetic pole N1 and the pick-off magnetic pole S2. Magnetic force is taken. Note that the magnetic force of the N pole was positive and the magnetic force of the S pole was negative with respect to the horizontal axis. In FIG. 7, when the magnetic shaft 21 is not arranged, the magnetic force distribution 36 is as shown by the solid line in FIG. 7, whereas when the magnetic shaft 21 is arranged, the magnetic force distribution is shown as shown by the broken line in FIG. 37 changes. That is, before and after the magnetic force distributions 36 and 37, the sum of the area of the N pole magnetic force and the area of the S pole magnetic force does not change. The magnetic force increases between the position of the transport magnetic pole N1 where the magnetic shaft 21 is disposed and the position of the adjacent developing magnetic pole S1.

Therefore, in the developing device Gy of Example 1, it is possible to reinforce the magnetic force of the developing magnetic pole S1 with the magnetic shaft 21 disposed on the transport magnetic pole N1.
In recent years, the developing device Gy has been downsized. When the developing device Gy is reduced in size, the developing roll R0y is also reduced in size, and the magnet roll 11 is also reduced in size. When the magnet roll 11 is reduced in size, the volume of the magnet is reduced and it is difficult to ensure a strong magnetic force. When the magnetic force is weakened, the force for attracting the carrier contained in the developer is weakened in the development region Q2y, and the carrier may move to the photosensitive drum PRy.

Here, it is conceivable to adjust the magnetic pole angle to ensure the magnetic flux density of the developing magnetic pole. However, the magnetic pole angle has an optimum angle depending on the shape of the developing device Gy, the positional relationship with the photosensitive drum PRy, and the like. Different. Therefore, if the angle is adjusted in order to secure the magnetic flux density of the developing magnetic pole, the positional relationship of the developing device Gy or the like may not be supported.
On the other hand, in the first embodiment, the developing magnetic pole S1 can be strengthened only by arranging the magnetic shaft 21. Therefore, even if the developing device is downsized, it is possible to ensure the magnetic density of the developing magnetic pole S1.

In the first embodiment, the magnetic shaft 21 is disposed inside the half width 23. When the shaft 21 is disposed outside the half width 23, the deviation from the peak position of the transport magnetic pole N1 increases. Therefore, the magnetic flux density of the transport magnetic pole N1 becomes difficult to concentrate, and the effect of increasing the magnetic force of the developing magnetic pole S1 is reduced. On the other hand, in Example 1, the magnetic shaft 21 is disposed inside the half width 23, the magnetic flux density of the transport magnetic pole N1 tends to concentrate, and the magnetic force of the developing magnetic pole S1 tends to become strong.
Further, the magnetic shaft 21 of the first embodiment is disposed in a region closer to the position 24 that is twice the radius of the developing sleeve 12. If the distance is greater than the position 24 that is twice the radius, the magnetic shaft 21 is too far from the transport magnetic pole N1. If the magnetic shaft 21 is too far from the transport magnetic pole N1, the magnetic flux density of the transport magnetic pole N1 becomes difficult to concentrate, and the effect of increasing the magnetic force of the developing magnetic pole S1 is reduced. On the other hand, in Example 1, the magnetic shaft 21 is disposed closer to the position 24 that is twice the radius. Therefore, the magnetic flux density of the transport magnetic pole N1 tends to concentrate and the magnetic force of the developing magnetic pole S1 tends to increase.

  Further, the magnetic shaft 21 of the first embodiment is disposed at a position farther from the position 26 of the gap between the developing sleeve 12 and the trimmer 13. When the magnetic shaft 21 is installed at a position closer to the gap 26 between the developing sleeve 12 and the trimmer 13, the magnetic shaft 21 comes into contact with the developer held on the surface of the developing sleeve 12. Therefore, the developer may come off from the developing sleeve 12 and float due to contact with the magnetic shaft 21 to contaminate the inside of the copying machine U. On the other hand, in the first embodiment, the magnetic shaft 21 is further away from the position 26 of the gap between the developing sleeve 12 and the trimmer 13 and contact with the developer is reduced. Therefore, it is possible to prevent the inside of the copying machine U from becoming dirty.

  Furthermore, the cross-sectional area of the magnetic shaft 21 of Example 1 is set to be more than half of the cross-sectional area of the region 27. When the cross-sectional area of the magnetic shaft 21 is small, the magnetic capacity of the magnetic shaft 21 is small. Therefore, the concentrated magnetism from the transport magnetic pole N1 cannot be held. That is, the concentration of the magnetic flux density becomes insufficient, and the effect of increasing the magnetic force of the developing magnetic pole S1 is reduced. On the other hand, the magnetic shaft 21 of Example 1 has a sufficiently large cross-sectional area and a sufficiently large magnetic capacity. Therefore, the effect of increasing the magnetic force of the developing magnetic pole S1 can be sufficiently obtained.

(Experimental example)
Next, an experiment was performed to confirm the effect of Example 1.
FIG. 8 is an explanatory diagram of the experimental results of the experimental example, and is a bar graph of the experimental results obtained by measuring the increase in the magnetic flux density of the developing magnetic pole for experimental example 1, comparative example 1, and comparative example 2.
FIG. 9 is an explanatory diagram of the experimental results of the experimental example, in which the horizontal axis represents the peak value of the magnetic flux density of the transport magnetic pole and the vertical axis represents the increase in the magnetic flux density of the developing magnetic pole.
In Experimental Example 1, the experiment was performed with the configuration of Example 1. That is, the magnetic shaft 21 was installed at a position facing the transport magnetic pole N1. In Experimental Example 1, a magnetic flux density having a peak value of 85 [mT] of the magnetic pole N1 was used. The increase in the magnetic flux density of the developing magnetic pole was measured by measuring the increase relative to the state in which neither the magnetic shaft 21 nor the trimmer 13 was arranged. At this time, the increase in the magnetic flux density of the developing magnetic pole was 6 [mT] as shown in FIGS.

In Comparative Example 1, an increase in the magnetic flux density of the developing magnetic pole in the state where the magnetic shaft 21 was not provided in Experimental Example 1 was measured. In Comparative Example 1, as shown in FIG. 8, the increase in the magnetic flux density of the developing magnetic pole was 2 [mT].
In Comparative Example 2, an increase in the magnetic flux density of the developing magnetic pole was measured in the state in which only the magnetic shaft 21 was disposed without providing the magnetic trimmer 13 in Experimental Example 1. In Comparative Example 2, the increase in the magnetic flux density of the developing magnetic pole was 3 [mT].

In Comparative Example 3, the magnetic shaft 21 was not installed and the experiment was performed with the trimmer 13 installed, as compared to Experimental Example 1. In Comparative Example 3, developing rolls R0y to R0k different from those in Experimental Example 1 were used, and those having a peak value of the magnetic flux density of the transport magnetic pole N1 of 75 [mT] were used. In Comparative Example 3, the magnetic flux density was measured at three locations, both in the axial direction and at the central portion. At this time, the increase in the magnetic flux density of the developing magnetic pole was 4 to 5 [mT].
In Comparative Example 4, an experiment was performed in the same manner as in Comparative Example 3 except that the peak value of the magnetic flux density of the transport magnetic pole N1 was 48 [mT]. In Comparative Example 4, the increase in the magnetic flux density of the developing magnetic pole was 0 to 2 [mT].
In Comparative Example 5, an experiment was performed in the same manner as in Comparative Example 3 except that the peak value of the magnetic flux density of the transport magnetic pole N1 was 45 [mT]. In Comparative Example 5, the increase in the magnetic flux density of the developing magnetic pole was 0 to 1 [mT].

In Comparative Example 6, an experiment was performed in the same manner as in Comparative Example 3 except that the peak value of the magnetic flux density of the transport magnetic pole N1 was 45 [mT]. In Comparative Example 6, the increase in the magnetic flux density of the developing magnetic pole was 0 [mT].
In Comparative Example 7, an experiment was performed in the same manner as in Comparative Example 3 except that the peak value of the magnetic flux density of the transport magnetic pole N1 was 65 [mT]. In Comparative Example 7, the increase in the magnetic flux density of the developing magnetic pole was 2 to 4 [mT].
In Comparative Example 8, an experiment was performed in the same manner as in Comparative Example 3 except that the peak value of the magnetic flux density of the transport magnetic pole N1 was 45 [mT]. In Comparative Example 8, the increase in the magnetic flux density of the developing magnetic pole was 0 to -1 [mT].

  Therefore, as a result of the experiment, it was confirmed from the comparison between Experimental Example 1 and Comparative Example 1 that the magnetic flux density of the developing magnetic pole was increased when the magnetic shaft 21 was provided. From the comparison between Experimental Example 1 and Comparative Examples 1 and 2, the magnetic shaft 21 is more effective than the case where the magnetic trimmer 13 is installed, and the magnetic trimmer 13 and the magnetic shaft 21 are more effective. It was confirmed that the effect was enhanced by providing both of these. Further, from the results of Comparative Examples 1 and 3-8, the provision of the magnetic trimmer 13 also has a certain effect. From the results of Experimental Example 1 and Comparative Examples 1 and 2, the magnetic shaft 21 is compared in Comparative Examples 3 to 8. It was also confirmed that further effects are expected when added.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Modification examples (H01) to (H06) of the present invention are exemplified below.
(H01) Although the copying machine as an example of the image forming apparatus has been illustrated in the above embodiment, the present invention is not limited to this. For example, the copying machine is configured by a printer, a FAX, or a multifunction machine having a plurality or all of these functions. It is also possible.
(H02) In the above embodiment, the copying machine U has exemplified the configuration in which four color developers are used. However, the present invention is not limited to this. For example, a single color image forming apparatus, five or more colors, or three colors or less. The present invention can also be applied to a multicolor image forming apparatus.

(H03) In the above embodiment, the specific numerical values and material names exemplified in the embodiment can be arbitrarily changed according to the design and specifications.
(H04) In the above embodiment, a cylindrical shaft is illustrated as an example of the magnetic member, but the present invention is not limited to this. For example, any shape capable of concentrating magnetic force, such as a plate having a quadrangular cross section or a triangular cross section, can be employed.
(H05) In the above-described embodiment, the material having no magnetic force is exemplified as an example of the magnetic member. However, the present invention is not limited to this, and it is also possible to use a magnetic material having magnetic force, so-called permanent magnet.

(H06) In the above embodiment, the magnetic shaft 21 is disposed inside the half width 23, inside the position twice the radius of the developing sleeve 12, and outside the position 26 of the gap between the developing sleeve 12 and the trimmer 13. However, the present invention is not limited to this. Depending on the configuration, design, specifications, and the like of the developing device Gy, a configuration in which any or all of these conditions are not satisfied may be employed. Further, the cross-sectional area of the magnetic shaft 21 is desirably half or more of the region 27, but may be half or less.

11: Magnet member,
12 ... Rotating member,
13 ... restricting member,
21 ... Magnetic member,
23 ... An angle having a magnetic flux density more than half of the peak value of the magnetic flux density,
24 ... twice the radius of the rotating member,
F: Fixing device,
Gy, Gm, Gc, Gk ... developing device,
LHy, LHm, LHc, LHk ... latent image forming device,
N1 ... adjacent magnetic pole,
PRy, PRm, PRc, PRk ... Image carrier,
R0y, R0m, R0c, R0k ... developer holder,
S ... medium
S1: Development magnetic pole,
T1 + T2 + B ... transfer device,
U: Image forming apparatus.

Claims (4)

A latent image formed on the surface of the image carrier, comprising: a magnet member that is supported in a non-rotatable manner; and a rotating member that surrounds the outer periphery of the magnet member and rotates while holding a developer on the surface. A developer holder for developing
A developing magnetic pole disposed at a position corresponding to the image carrier, and an adjacent magnetic pole disposed adjacent to the developing magnetic pole with respect to the rotation direction of the rotating member and having a polarity opposite to the developing magnetic pole. The magnet member;
A magnetic member disposed opposite to the adjacent magnetic pole and having magnetism;
The surface of the rotating member is disposed on the upstream side of the position where the image holding member and the rotating member face each other with respect to the rotation direction of the rotating member, with a gap between the rotating member and the rotating member. A regulating member that regulates the amount of developer held in
In a cross section perpendicular to the rotation axis of the developer holder, an angular region having a magnetic flux density that is half or more of the peak value of the magnetic flux density of the magnetic field formed in the normal direction of the developer holder, and the rotation member The magnetic member having a cross-sectional area of more than half of a cross-sectional area of a region surrounded by a position twice the radius and a position corresponding to the interval between the rotating member and the regulating member;
A developing device comprising: In an area having an angle having a magnetic flux density more than half of the peak value of the magnetic flux density of the magnetic field formed in the normal direction of the developer holder, and in an area closer to twice the radius of the rotating member The magnetic member disposed,
The developing device according to claim 1, further comprising: The surface of the rotating member is disposed on the upstream side of the position where the image holding member and the rotating member face each other with respect to the rotation direction of the rotating member, with a gap between the rotating member and the rotating member. A regulating member that regulates the amount of developer held in
Compared to the gap between the rotating member and the regulating member, the magnetic member in which the gap between the rotating member and the rotating member is set wide,
The developing device according to claim 1, further comprising: An image carrier,
A latent image forming apparatus for forming a latent image on the surface of the image carrier;
The developing device according to any one of claims 1 to 3 , wherein a latent image on the surface of the image carrier is developed into a visible image;
A transfer device for transferring a visible image of the surface of the image carrier to a medium;
A fixing device for fixing a visible image on the surface of the medium;
An image forming apparatus comprising:

Images